Receiving method and receiver

ABSTRACT

BB input units input baseband received signals. An initial weight data setting unit sets weighting coefficients to be utilized in the interval of a training signal as initial weighting coefficients. A gap compensating unit compensates control weighting coefficients with a gap error signal and outputs the updated weighting coefficients acquired as a result of the compensation. A weight switching unit selects the initial weighting coefficients in the interval of the training signal and selects the updated weighting coefficients in the interval of the data signal. Then the weight switching unit outputs the selected initial weighting coefficients and updated weighting coefficients as the weighting coefficients. A synthesizing unit weights the baseband received signals with the weighting coefficients and then sums them up.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a receiving technology. Itparticularly relates to a receiving method and a receiving apparatuswhich controls a weighting coefficient for synthesizing radio signalsreceived by a plurality of antennas.

[0003] 2. Description of the Related Art

[0004] In wireless communication, it is in general desired toeffectively use limited frequency resources. In order to use thefrequency resources effectively, radio waves of same frequency are, forexample, utilized as repeatedly as possible in short-range. In thiscase, however, communication quality degrades because of cochannelinterference caused by a radio base station or mobile terminal closelylocated, which utilizes the same frequency. As one technology forpreventing such communication quality degradation deriving from thecochannel interference, the adaptive array antenna technology can benamed.

[0005] In the adaptive array antenna technology, signals received by aplurality of antennas are respectively weighted with different weightingcoefficients and synthesized. The weighting coefficients are adaptivelyupdated so that an error signal between a signal to be transmitted andthe signal after the synthesis might be small. Here, the signal to betransmitted is determined based on the signal after synthesis. In orderto update the weighting coefficients adaptively, the RLS (RecursiveLeast Squares) algorithm, the LMS (Least Mean Squares) algorithm or thelike is utilized. The RLS algorithm generally converges at high speed.The RLS algorithm, however, requires a high speed or a huge arithmeticcircuit since computation performed is very complicated. The LMSalgorithm can be realized with a simpler arithmetic circuit than that ofthe RLS algorithm. However, the convergence speed thereof is low.

[0006] Related Art List

[0007] 1. Japanese Patent Application Laid-open No. 2002-26788

[0008] In utilizing the adaptive array antenna for a radio mobileterminal, it is suitable to use the LMS algorithm for updating weightingcoefficients, since it is desirable that an arithmetic circuit is small.However, the convergence speed of the LMS algorithm is low in general.Thus, if it is desired to delay received signals to be synthesized untilthe LMS algorithm converges, processing delay becomes large andtherefore it is possibly impossible to use the adaptive array antenna ina real time application such as TV conference system where permissibledelay time is limited. On the other hand, a response characteristicgenerally degrades if the weighting coefficients at the timing where theLMS algorithm has not converged yet in order to diminish the processingdelay.

SUMMARY OF THE INVENTION

[0009] The inventor of the present invention has made the presentinvention in view of the foregoing circumstances and an object thereofis to provide a receiver having simple arithmetic circuits, of which theprocessing delay is small. It is also an object of the present inventionto provide a receiver of which the response characteristic hardlydegrades even in the case the weighting coefficients have not convergedyet. Moreover, it is also an object of the present invention to providea receiver which can switch a plural types of weighting coefficients.

[0010] A preferred embodiment according to the present invention relatesto a receiver. This receiver includes: an input unit which inputs aplurality of signals on which a processing is to be performed; aswitching unit which switches a plurality of weighting coefficients bywhich the plurality of inputted signals are multiplied between aplurality of first weighting coefficients to be temporarily utilized anda plurality of second weighting coefficients which have higheradaptabilities; a controller which instructs the switching unit toswitch the weighting coefficients between the plurality of firstweighting coefficients and the plurality of second weightingcoefficients; and a synthesizer which synthesizes results ofmultiplications, where the multiplications are performed on theplurality of inputted signals and the plurality of weightingcoefficients.

[0011] The plurality of weighting coefficients include (A, B, C, D) ofwhich the number of terms is equal to that of the plurality of signals,where the results of multiplications between them and (X1, Y1), (X2, Y2)become (AX1, BY1) and (CX2, DY2). The plurality of weightingcoefficients also include (A, B) of which the number of terms isdifferent from that of the plurality of signals, where the results ofmultiplications become (AX1, BY1) and (AX2, BY2).

[0012] The receiver described above enables to acquire a responsecharacteristic optimal in each timing by switching the weightingcoefficients which have different characteristics.

[0013] Another preferred embodiment of the present invention alsorelates to a receiver. The receiver includes: an input unit which inputsa plurality of signals on which a processing is to be performed; aswitching unit which switches a plurality of weighting coefficients bywhich the plurality of inputted signals are multiplied between aplurality of first weighting coefficients and a plurality of secondweighting coefficients; a controller which instructs the switching unitto switch the weighting coefficients between the plurality of firstweighting coefficients and the plurality of second weightingcoefficients in a prescribed interval, where the plurality of signalsare inputted in a sequential manner during the interval; and asynthesizer which synthesizes results of multiplications, where themultiplications are performed on the plurality of inputted signals andthe plurality of weighting coefficients.

[0014] The “sequential manner” merely means that the known receivedsignal is sequential. As long as the signals are inputted sequentially,the time length does not necessarily need to be long but may be short.Moreover, the sequential manner here may include a case where thesignals are inputted in a discrete manner in accordance with a certainrule, if the apparatus recognizes the rule. That is, the “sequentialmanner” here includes every case where the receiver can recognize themanner of inputting the signals as “sequential” one.

[0015] The plurality of first weighting coefficients may be set in amanner that, as results of multiplications by the plurality of inputtedsignals, a multiplication result corresponding to one signal among theplurality of inputted signals becomes effective. The one signal amongthe plurality of inputted signals may be a signal having a largest valueamong the plurality of inputted signals. The plurality of firstweighting coefficients may be set by utilizing the plurality of secondweighting coefficients which have already been set.

[0016] The receiver may further include: a weighting coefficientupdating unit which updates a plurality of third weighting coefficientsadaptively based on the plurality of inputted signals; a gap estimatorwhich estimates gaps between the plurality of first weightingcoefficients and the plurality of third weighting coefficients byperforming a correlation processing between at least one of theplurality of inputted signals and a known signal; and a gap compensatorwhich generates the plurality of second weighting coefficients bycompensating the plurality of third weighting coefficients based on theestimated gaps.

[0017] The signals inputted during the prescribed interval in thesequential manner may include signals having different characteristicsand the controller may instruct to switch the weighting coefficientsbetween the first weighting coefficients and the second weightingcoefficients when it is detected a shift point where the characteristicsof the signals change. The controller may input sequentially theplurality of third weighting coefficients updated in the weightcoefficient updating unit and may instruct the switching unit to switchthe weighting coefficients between the first weighting coefficients andthe second weighting coefficients when fluctuation of the plurality ofthird weighting coefficients converges within a prescribed range.

[0018] The receiver described above enables to acquire a responsecharacteristic optimal in each time by switching the weightingcoefficients which have different characteristics during the interval.

[0019] Still, another preferred embodiment according to the presentinvention relates to a receiving method. This method includes: inputtinga plurality of signals on which a processing is to be performed;switching a plurality of weighting coefficients by which the pluralityof inputted signals are multiplied between a plurality of firstweighting coefficients to be temporarily utilized and a plurality of asecond weighting coefficients which have higher adaptabilities; givingan instruction of switching the weighting coefficients between theplurality of first weighting coefficients and the plurality of secondweighting coefficients; and synthesizing results of multiplications,where the multiplications are performed on the plurality of inputtedsignals and the plurality of weighting coefficients.

[0020] Still another preferred embodiment according to the presentinvention relates to a receiving method. This method includes: inputtinga plurality of signals on which a processing is to be performed;switching a plurality of weighting coefficients by which the pluralityof inputted signals are multiplied between a plurality of firstweighting coefficients and a plurality of second weighting coefficients;giving an instruction of switching the weighting coefficients betweenthe plurality of first weighting coefficients and the plurality ofsecond weighting coefficients in a prescribed interval, where theplurality of signals are inputted in a sequential manner during theinterval; and synthesizing results of multiplications, where themultiplications are performed on the plurality of inputted signals andthe plurality of weighting coefficients.

[0021] The plurality of first weighting coefficients may be set in amanner that, as results of multiplications by the plurality of inputtedsignals, a multiplication result corresponding to one signal among theplurality of inputted signals becomes effective. The one signal amongthe plurality of inputted signals may be a signal having a largest valueamong the plurality of inputted signals. The plurality of firstweighting coefficients may be set by utilizing the plurality of secondweighting coefficients which have already been set.

[0022] The receiving method may further include: updating a plurality ofthird weighting coefficients adaptively based on the plurality ofinputted signals; estimating gaps between the plurality of firstweighting coefficients and the plurality of third weighting coefficientsby performing a correlation processing between at least one of theplurality of inputted signals and a known signal; and generating theplurality of second weighting coefficients by compensating the pluralityof third weighting coefficients based on the estimated gaps.

[0023] The signals inputted during the prescribed interval in thesequential manner may include signals having different characteristics.In giving the instruction of switching the weighting coefficientsbetween the first weighting coefficients and the second weightingcoefficients, the instruction may be given when it is detected a shiftpoint where the characteristics of the signals change. The plurality ofthird weighting coefficients updated may be inputted sequentially ingiving the instruction of switching the weighting coefficients betweenthe first weighting coefficients and the second weighting coefficients,and the instruction may be given when fluctuation of the plurality ofthird weighting coefficients converges within a prescribed range.

[0024] Yet another preferred embodiment of the present invention relatesto a program. The program includes: inputting a plurality of signals onwhich a processing is to be performed; switching a plurality ofweighting coefficients by which the plurality of inputted signals aremultiplied between a plurality of first weighting coefficients to betemporarily utilized and a plurality of a second weighting coefficientswhich have higher adaptabilities; giving an instruction of switching theweighting coefficients between the plurality of first weightingcoefficients and the plurality of second weighting coefficients; andsynthesizing results of multiplications, where the multiplications areperformed on the plurality of inputted signals and the plurality ofweighting coefficients.

[0025] Still another preferred embodiment according to the presentinvention relates to a program method. This program includes: inputtinga plurality of signals on which a processing is to be performed;switching a plurality of weighting coefficients by which the pluralityof inputted signals are multiplied between a plurality of firstweighting coefficients and a plurality of second weighting coefficients;giving an instruction of switching the weighting coefficients betweenthe plurality of first weighting coefficients and the plurality ofsecond weighting coefficients in a prescribed interval, where theplurality of signals are inputted in a sequential manner during theinterval; and synthesizing results of multiplications, where themultiplications are performed on the plurality of inputted signals andthe plurality of weighting coefficients.

[0026] The plurality of first weighting coefficients may be set in amanner that, as results of multiplications by the plurality of inputtedsignals, a multiplication result corresponding to one signal among theplurality of inputted signals becomes effective. The one signal amongthe plurality of inputted signals may be a signal having a largest valueamong the plurality of inputted signals. The plurality of firstweighting coefficients may be set by utilizing the plurality of secondweighting coefficients which have already been set.

[0027] The receiving method may further include: updating a plurality ofthird weighting coefficients adaptively based on the plurality ofinputted signals; estimating gaps between the plurality of firstweighting coefficients and the plurality of third weighting coefficientsby performing a correlation processing between at least one of theplurality of inputted signals and a known signal; and generating theplurality of second weighting coefficients by compensating the pluralityof third weighting coefficients based on the estimated gaps.

[0028] The signals inputted during the prescribed interval in thesequential manner may include signals having different characteristics.In giving the instruction of switching the weighting coefficientsbetween the first weighting coefficients and the second weightingcoefficients, the instruction may be given when it is detected a shiftpoint where the characteristics of the signals change. The plurality ofthird weighting coefficients updated may be inputted sequentially ingiving the instruction of switching the weighting coefficients betweenthe first weighting coefficients and the second weighting coefficients,and the instruction may be given when fluctuation of the plurality ofthird weighting coefficients converges within a prescribed range.

[0029] It is to be noted that any arbitrary replacement or substitutionof the above-described structural components and the steps, expressionsreplaced or substituted in part or whole between a method and anapparatus as well as addition thereof, and expressions changed to acomputer program, recording medium or the like are all effective as andencompassed by the present embodiments.

[0030] Moreover, this summary of the invention does not necessarilydescribe all necessary features so that the invention may also besub-combination of these described features.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 shows a structure of a communication system according to afirst embodiment of the present invention.

[0032]FIG. 2 shows a burst format according to the first embodiment ofthe present invention.

[0033]FIG. 3 shows a burst format according to the first embodiment ofthe present invention.

[0034]FIG. 4 shows a structure of a receiver according to the firstembodiment of the present invention.

[0035]FIG. 5 shows a structure of a first pre-processing unit shown inFIG. 4.

[0036]FIG. 6 shows a structure of the first pre-processing unit shown inFIG. 4.

[0037]FIG. 7 shows a structure of the first pre-processing unit shown inFIG. 4.

[0038]FIG. 8 shows a structure of a timing detection unit shown in FIGS.5, 6 and 7.

[0039]FIG. 9 shows a structure of a rising edge detection unit shown inFIG. 4.

[0040]FIG. 10 shows an operation procedure of the rising edge detectionunit shown in FIG. 9.

[0041]FIG. 11 shows a structure of an antenna determination unit shownin FIG. 4.

[0042]FIG. 12 shows a structure of a first weight computation unit shownin FIG. 4.

[0043]FIG. 13 shows a structure of a gap measuring unit shown in FIG. 4.

[0044]FIG. 14 shows a structure of a gap compensating unit shown in FIG.4.

[0045]FIG. 15 shows a structure of a synthesizing unit shown in FIG. 4.

[0046]FIG. 16 shows a structure of a receiver according to a secondembodiment of the present invention.

[0047]FIG. 17 shows a structure of an antenna determination unit shownin FIG. 16.

[0048]FIG. 18 shows a structure of a gap measuring unit shown in FIG.16.

[0049]FIG. 19 shows a structure of a frequency error estimation unitshown in FIG. 18.

[0050]FIG. 20 shows a structure of a gap measuring unit shown in FIG.16.

DETAILED DESCRIPTION OF THE INVENTION

[0051] The invention will now be described based on the preferredembodiments, which do not intend to limit the scope of the presentinvention, but exemplify the invention. All of the features and thecombinations thereof described in the embodiment are not necessarilyessential to the invention.

[0052] First Embodiment

[0053] The first embodiment of the present invention relates to areceiver provided with an adaptive array antenna which receives radiosignals with a plurality of antennas as burst signals and synthesizesthe received signals with weighting them respectively by differentweighting coefficients. The burst signal is composed of a known trainingsignal which is disposed in the head part thereof and a data signal. Thereceiver, in order to reduce processing delay, synthesizes the receivedsignals by weighting them with the weighting coefficients withoutscarcely delaying them. The weighting coefficients are updated by theLMS algorithm one after another. As the weighting coefficients in thetraining signal interval, however, precedently prepared weightingcoefficients of an omni antenna pattern are utilized since it is oftenthe case that the weighting coefficients have not converged yet in theinitial period of the training signal interval. Weighting coefficientsof adaptive array antenna pattern, which are updated by the LMSalgorithm, are utilized as the weighting coefficients in the interval ofthe data signal.

[0054]FIG. 1 shows a communication system including a transmitter 100and a receiver 106 according to the first embodiment of the presentinvention. The transmitter 100 includes a modulator 102, a RF unit 104,and an antenna 132. The receiver 106 includes a first antenna 134 a, asecond antenna 134 b, a n-th antenna 134 n, a RF unit 108, a signalprocessing unit 110, and a demodulator 112. Here the first antenna 134a, the second antenna 134 b and the n-th antenna 134 n are genericallynamed antennas 134.

[0055] The modulator 102 modulates an information signal to betransmitted and generates the transmission signal (hereinafter onesignal included in the transmission signal is also called as a“symbol”). Any arbitrary modulation scheme may be utilized, such as QPSK(Quadri Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation),GMSK (Gaussian filtered Minimum Shift Keying). In the followingembodiments, examples are described where the QPSK is utilized.Moreover, in a case of a multi carrier communication, the transmitter100 is provided with the plurality of modulators 102 or inverse Fouriertransform units. In a case of a spectrum spreading communication, themodulator 102 is provided with a spreading unit.

[0056] The RF unit 104 transforms the transmission signal into radiofrequency signal. A frequency transformation unit, a power amplifier, afrequency oscillator and so forth are included therein.

[0057] The antenna 132 of the transmitter 100 transmits the radiofrequency signals. The antenna may have arbitrary directivity and thenumber of the antennas may also be arbitrary.

[0058] The antennas 134 of the receiver 106 receive the radio frequencysignals. In this embodiment, the number of the antennas 134 is n. Whenit is described in this embodiment that the receiver has a n-thcomponent thereof, it means that the number of the components providedto the receiver 106 is same as the number of the antennas 134, where thefirst, second, . . . n-th component basically performs same operation inparallel.

[0059] The RF unit 108 transforms the radio frequency signals intobaseband received signals 300. A frequency oscillator and so forth areprovided to the RF unit 108. In a case of the multi carriercommunication, the RF unit 108 is provided with a Fourier transformunit. In a case of the spectrum spreading communication, the RF unit 108is provided with a despreading unit.

[0060] The signal processing unit 110 synthesizes the baseband receivedsignals 330 with respectively weighting by the weighting coefficientsand controls each weighting coefficient adaptively.

[0061] The demodulator 112 demodulates the synthesized signals andperforms decision on the transmitted information signal. The demodulator112 may also be provided with a delay detection circuit or a carrierrecovery circuit for coherent detection.

[0062]FIG. 2 and FIG. 3 show other burst formats respectively utilizedin different communication systems corresponding to the communicationsystem shown in FIG. 1. Training signals and data signals included inthe burst signals are also shown in those figures. FIG. 2 shows a burstformat utilized in a traffic channel of the Personal Handyphone System.A preamble is placed in initial 4 symbols of the burst, which isutilized for timing synchronization. The signals of the preamble and aunique word can serve as a known signal for the signal processing unit110, therefore the signal processing unit 110 can utilize the preambleand the unique word as the training signal. Data and CRC both followingafter the preamble and the unique word are unknown for the signalprocessing unit 110 and correspond to the data signal.

[0063]FIG. 3 shows a burst format utilized in a traffic channel of theIEEE 802.11a, which is one type of wireless LAN (Local Area Network).The IEEE 802.11a employs OFDM (Orthogonal Frequency DivisionMultiplexing) modulation scheme. In the OFDM modulation scheme, the sizeof the Fourier transform and the number of the symbols of the guardinterval are summated and the summation forms a unit. It is to be notedthat this one unit is described as an OFDM symbol in this embodiment. Apreamble is placed in initial 4 OFDM symbols of the burst, which ismainly utilized for timing synchronization and carrier recovery. Thesignals of the preamble can serve as a known signal for the signalprocessing unit 110, therefore the signal processing unit 110 canutilize the preamble as the training signal. Header and Data bothfollowing after the preamble are unknown for the signal processing unit110 and correspond to the data signal.

[0064]FIG. 4 shows a structure of the receiver 106 shown in FIG. 1. TheRF unit 108 includes a first pre-processing unit 114 a, a secondpre-processing unit 114 b, . . . and a n-th pre-processing unit 114 n,which are generically named pre-processing units 114. The signalprocessing unit 110 includes: a first BB input unit 116 a, a second BBinput unit 116 b, . . . and a n-th BB input unit 116 n which aregenerically named BB input units 116; a synthesizing unit 118; a firstweight computation unit 120 a, a second weight computation unit 120 b, .. . and a n-th weight computation unit 120 n which are generically namedweight computation units 120; a rising edge detection unit 122; acontrol unit 124; a training signal memory 126; an antenna determinationunit 10; an initial weight data setting unit 12; a gap measuring unit14, a gap compensating unit 16; a weight switching unit 18. Thedemodulator 112 includes a synchronous detection unit 20, a decisionunit 128 and a summing unit 130.

[0065] Moreover the signals utilized in the receiver 106 include: afirst baseband received signal 300 a, a second baseband received signal300 b, . . . and n-th baseband received signal 300 n which aregenerically named the baseband received signals 300; a training signal302; a control signal 306; an error signal 308; a first controlweighting coefficient 310 a, a second control weighting coefficient 310b, . . . and a n-th control weighting coefficient 310 n which aregenerically named control weighting coefficients 310; an antennaselection signal 314; a gap error signal 316; a first updated weightingcoefficient 318 a, a second updated weighting coefficient 318 b, . . .and a n-th updated weighting coefficient 318 n which are genericallynamed updated weighting coefficients 318; a first initial weightingcoefficient 320 a, a second initial weighting coefficient 320 b, . . .and a n-th initial weighting coefficient 320 n which are genericallynamed initial weighting coefficients 320; and a first weightingcoefficient 322 a, a second weighting coefficient 322 b, . . . and an-th weighting coefficient 322 n which are generically named weightingcoefficients 322.

[0066] The pre-processing units 114 translates the radio frequencysignals into the baseband received signals 300.

[0067] The rising edge detection unit 122 detects the starts of theburst signals which serve as a trigger of the operation of the signalprocessing unit 110 from the baseband received signals 300. The timingsof the detected starts of the burst signals are informed to the controlunit 124. The control unit 124 computes timings when the interval of thetraining signal 302 ends, based on the timings of the starts of theburst signals. These timings are notified to each unit as controlsignals 306 in accordance with necessity.

[0068] The antenna determination unit 10 measures the electric power ofeach baseband received signal 300 after the interval of the trainingsignal 302 is started in order to select one antenna 134 to be madeeffective in the interval of the training signal 302 and then determinesthe one baseband received signal 300 of which the electric power becomesis largest. Moreover, the antenna determination unit 10 outputs thisinformation as the antenna selection signal 314.

[0069] The initial weight data setting unit 12 sets the weightingcoefficients 322 utilized in the interval of the training signal 302 asthe initial weighting coefficients 320. The initial weight data settingunit 12 makes only one initial weighting coefficient 302 effective bysetting the value of the one initial weighting coefficient 320 as 1 andby setting the values of the other weighting coefficients 320 as 0. Theone initial weighting coefficient 320 to be made effective is decidedaccording to the antenna selection signal 314.

[0070] The training signal memory 126 stores the training signal 302 andoutputs the training signal in accordance with necessity.

[0071] The weight computation unit 120 updates the control weightingcoefficients 310 based on the baseband received signals 300 andafter-mentioned error signal 308 by the LMS algorithm.

[0072] The gap measuring unit 14, based on the baseband received signals300 and the training signal 302, estimates the gap between the resultsof a synthesis processing performed in the after-mentioned synthesizingunit 118, wherein one result is acquired by performing the synthesizingprocessing on the initial weighting coefficients 320 and basebandreceived signals 300 and the other is acquired by performing thesynthesizing processing on the control weighting coefficients 310 andthe baseband received signals 300. The synthesis result acquired byutilizing the initial weighting coefficients 320 is the basebandreceived signal 300 as it is, which is corresponding to one antenna 134.Therefore following expression (1) can be acquired. Here, it is presumedthat the one antenna 134 is an i-th antenna 134.

X _(i)(t)=h _(i) S(t)exp(jΔωt)+n _(i) t  (1)

[0073] Here, hi is the response characteristic of the radio interval,S(t) is the transmission signal, Δω is the frequency offset between thefrequency oscillators of the transmitter 100 and the receiver 106, andni(t) is a noise. On the other hand, a control weighting coefficient 310wi updated from the head region of the burst signal is given by:

93 h _(i) w _(i)=1  (2)

[0074] Here, it is presumed assumed that the control weightingcoefficients have already converged sufficiently.

[0075] By performing the synthesis processing based on the ground of theabove-described expression (2), following result of the synthesisprocessing can be acquired.

y(t)=S(t)exp (jΔωt)+n(t)  (3)

[0076] By comparing the synthesis results shown in (1) and (3), a gaperror signal 316C is given by:

[0077] C=h_(i)  (4)

[0078] The gap compensating unit 16 compensates the control weightingcoefficients 310 with the gap error signal 316 and outputs the result ofthe compensation as the updated weighting coefficients 318.

[0079] The weight switching unit 18, based on the instruction of thecontrol signal 306, selects the initial weighting coefficients 320 inthe interval of the training signal 302 and selects the updatedweighting coefficients 318 in the interval of the data signal. Then, theweight switching unit 18 outputs them as the weighting coefficients 322.

[0080] The synthesizing unit 118 weights the baseband received signals300 with the weighting coefficients 322 and then sums them up.

[0081] The synchronous detection unit 20 performs synchronous detectionon the synthesized signals and also performs a carrier recoverynecessary for the synchronous detection.

[0082] The decision unit 128 decides the transmitted information signalby comparing the signal acquired by the summation to a pre-determinedthreshold value. The decision may be either hard or soft.

[0083] The summing unit 130 generates the error signal 308 based on thedifference value between the synchronous detected signal and the decidedsignal, which is to be utilized in the LMS algorithm in the weightcomputation units 120. In an ideal situation, the error signal becomeszero since the LMS algorithm controls the weighting coefficients 310 sothat the error signal 308 might become small.

[0084]FIG. 5 to FIG. 7 show various structures of the firstpre-processing unit 114 a. The first pre-processing unit 114 a in thereceiver 106 can accept and treat various signals in differentcommunication systems such as shown in FIG. 2 or FIG. 3, therefore thesignal processing unit 110 following thereafter can operate ignoring thedifference of the communication systems. The first pre-processing unit114 a in FIG. 5 is for the single carrier communication system shown inFIG. 2 such as Personal Handyphone System, cellular phone system or thelike. The first pre-processing unit 114 a in FIG. 5 includes a frequencytranslation unit 136, a quasi synchronous detector 138, an AGC(Automatic Gain Control) 140, an AD conversion unit 142, and a timingdetection unit 144. The first pre-processing unit 114 a shown in FIG. 6is for the spectrum spreading communication system such as the W-CDMA(Wideband-Code Division Multiple Access) or the wireless LAN implementedin relation to the IEEE 802.11b. In addition to the first pre-processingunit 114 a shown in FIG. 5, that shown in FIG. 6 further includes adespreading unit 172. The first pre-processing unit 114 a is for themulti carrier communication system shown in FIG. 3 such as the IEEE802.11a or the Hiper LAN/2. In addition to the first pre-processing unit114 a shown in FIG. 6, that shown in FIG. 7 further includes a Fouriertransform unit 174.

[0085] The frequency translation unit 136 translates the radio frequencysignal into one intermediate frequency signal, a plurality ofintermediate frequency signals or other signals. The quasi synchronousdetector 138 performs quadrature detection on the intermediate frequencysignal utilizing a frequency oscillator and generates a baseband analogsignal. Since the frequency oscillator included in the quasi synchronousdetector 138 operates independently from the frequency oscillatorprovided to the transmitter 100, the frequencies between the twooscillators differ from each other.

[0086] The AGC 140 automatically controls gains so that the amplitude ofthe baseband analog signal might become an amplitude within the dynamicrange of the AD conversion unit 142.

[0087] The AD conversion unit 142 converts the baseband analog signalinto a digital signal. Sampling interval for converting the basebandanalog signal to the digital signal is generally set to be shorter thansymbol interval in order to constrict the degradation of the signal.Here, the sampling interval is set to the half of the symbol interval(Hereinafter, the signal digitalized with this sampling interval isreferred to as a “high speed digital signal”).

[0088] The timing detection unit 144 selects a baseband received signal300 of an optimal sampling timing from the high speed digital signals.Alternatively, the timing detection unit 144 generates the basebandreceived signal 300 having the optimal sampling timing by performing asynthesis processing or the like on the high speed digital signals.

[0089] The despreading unit 172 shown in FIG. 6 performs correlationprocessing on the baseband received signal 300 based on a predeterminedcode series. The Fourier transform unit 174 in FIG. 7 performs theFourier transform on the baseband received signal 300.

[0090]FIG. 8 shows the structure of the timing detection unit 144. Thetiming detection unit 144 includes: a first delay unit 146 a, a seconddelay unit 146 b, . . . and a (n−1)-th delay unit 146 n−1 which aregenerically named delay units 146; a first multiplication unit 150 a, asecond multiplication unit 150 b, a (n−1)-th multiplication unit 150n−1, . . . and a n-th multiplication unit 150 n which are genericallynamed multiplication units 150; a first data memory 152 a, a second datamemory 152 b, a (n−1)-th data memory 152 n−1, . . . a n-th data memory152 n which are generically named data memories 152; a summing unit 154;a decision unit 156; a main signal delay unit 158; and a selecting unit160.

[0091] The delay units 146 delay the inputted high speed digital signalfor the correlation processing. The sampling interval of the high speeddigital signal is set to half of the symbol interval. However the delayquantity of the delay units 146 is set to the symbol interval, thereforethe high speed digital signal 150 is outputted from every other delayunit 146 to the multiplication units 150.

[0092] The data memories 152 store 1 symbol of each preamble signal forthe timing synchronism.

[0093] The multiplication units 150 perform multiplications on the highspeed digital signals and the preamble signals, and the results thereofare summed up by the summing unit 154.

[0094] The decision unit 156 selects an optimal sampling timing based onthe result of the summation. The sampling interval of the high speeddigital signal is half of the symbol signal and the interval of the highspeed digital signal utilized for the summation is equal to the symbolinterval, therefore there are two types of the summation results forevery other high speed digital signal corresponding to each shiftedsampling timing. The decision unit 156 compares the two types of thesummation results and decides a timing corresponding to larger summationresult as the optimal sampling timing. This decision should notnecessarily be made by comparing the two types of the summation resultsonce, but may be made by comparing them for several times.

[0095] The main signal delay unit 158 delays the high speed digitalsignal until the optimal sampling timing is determined by the decisionunit 156.

[0096] The selecting unit 160 selects a baseband received signal 300corresponding to the optimal sampling timing from the high speed digitalsignals. Here one high speed digital signal is selected sequentiallyfrom the two successive high digital speed signals.

[0097]FIG. 9 shows the structure of the rising edge detection unit 122included in the signal processing unit 110. The rising edge detectionunit 122 includes a power computation unit 162 and a decision unit 164.The power computation unit 162 computes the received power of eachbaseband received signal 300 and then sums up the received power of eachbaseband received signal to acquire the whole power of the signals whichare received by all the antennas 134.

[0098] The decision unit 164 compares the whole received power of thesignals with a predetermined condition and decides that the start of theburst signal is detected when the condition is satisfied.

[0099]FIG. 10 shows the operation of the rising edge detection unit 122.The decision unit 164 sets an internal counter T to zero (S10). Thepower computation unit 162 computes the received power from the basebandreceived signals 300 (S12). The determination unit 164 compares thereceived power with a threshold value. When the received power is largerthan the threshold value (Y in S14), the decision unit 164 adds 1 to theT (S16). When the T becomes larger than a predetermined value τ (Y inS18), it is decided that the start of the burst signal is detected. Theprocessing described-above is repeated until the start of the burstsignal is detected (N in S14, N in S18).

[0100]FIG. 11 shows the structure of the antenna determination unit 10.The antenna determination unit 10 includes: a first level measuring unit22 a, a second level measuring unit 22 b, . . . and a n-th levelmeasuring unit 22 n which are generically called level measuring units22; and a selecting unit 24.

[0101] The level measuring units 22 detect the start timing of the burstsignal based on the control signal 306 and measure the electric power ofeach baseband received signal 300 during prescribed interval from thestart timing.

[0102] The selecting unit 24 selects the baseband received signal 300which has the largest electric power by comparing the electric power ofeach baseband received signal 300 and then outputs a result as theantenna selection signal 314.

[0103]FIG. 12 shows the structure of the first weight computation unit120 a. The first weight computation unit 120 a includes a switching unit48, a complex conjugate unit 50, a main signal delay unit 52, amultiplication unit 54, a step size parameter memory 56, amultiplication unit 58, a summing unit 60, and a delay unit 62.

[0104] The switching unit 48 selects the training signal 302 in theinterval of the training signals 302 by detecting the start timing ofthe burst signal and the end timing of interval of the training signal302 based on the control signal 306 and then selects the error signal308 in the interval of the data signal.

[0105] The main signal delay unit 52 delays the first baseband receivedsignal 300 a so that the first baseband received signal 300 a mightsynchronize with the timing detected by the rising edge detection unit122.

[0106] The multiplication unit 54 generates a first multiplicationresult by multiplying the phase error 308 after complex conjugatetransform in the complex conjugate unit 50 by the first basebandreceived signal 300 a which is delayed by the main signal delay unit 52.

[0107] The multiplication unit 58 generates a second multiplicationresult by multiplying the first multiplication result by a step sizeparameter stored in the step size parameter memory 56. The secondmultiplication result is fed back by the delay unit 62 and the summingunit 60 and added to a new second multiplication result. The result ofthe summation is then sequentially updated by the LMS algorithm. Thissummation result is outputted as the first weighting coefficient 310 a.

[0108]FIG. 13 shows the structure of the gap measuring unit 14. The gapmeasuring unit 14 includes a complex conjugate unit 44, a selecting unit64, a buffer unit 66 and a multiplication unit 68.

[0109] The selecting unit 64, based on the antenna selection signal 314,selects the baseband received signal 300 corresponding to the oneinitial weighting coefficient 320 which has been made effective in theinterval of the training signal 302.

[0110] The buffer unit 66 detects the start timing of the burst signalbased on the control signal 306 and outputs the baseband received signal300 at the start timing.

[0111] The multiplication unit 68 multiplies the training signal 302after the complex conjugate processing in the complex conjugate unit 44by the one baseband received signal 300 outputted from the buffer unit66 and then outputs the gap error signal 316. Here, it is presumed thatboth the training signal 302 and baseband received signal 300 are thehead signal of the burst signal.

[0112]FIG. 14 shows the structure of the gap compensating unit 16. Thegap compensating unit 16 includes a first multiplication unit 70 a, asecond multiplication unit 70 b, . . . and a n-th multiplication unit 70n which are generically named multiplication units 70.

[0113] The multiplication units 70 detect the end timing of the intervalof the training signal 302 based on the control signal 306. Then themultiplication units 70 multiply the control weighting coefficients 310by the gap error signal 316 and outputs the updated weightingcoefficients 318.

[0114]FIG. 15 shows the structure of the synthesizing unit 118 which isincluded in the signal processing unit 110. The synthesizing unit 118includes: a first delay unit 166 a, a second delay unit 166 b, . . . anda n-th delay unit 166 n which are generically named delay units 166; afirst multiplication unit 168 a, a second multiplication unit 168 b, . .. and a n-th multiplication unit 168 n which are generically namedmultiplication units 168; and a summing unit 170.

[0115] Since the delay time of the delay units 166 is from the detectionof the head of the burst signal by the rising edge detection unit 122until setting the weighting coefficients 322 by the initial weight datasetting unit 12 via the weight switching unit 18, the processing delayof the delay units 166 can be ignored in general. Therefore,synthesizing processing with less processing delay can be realized.

[0116] The multiplication units 168 multiply the baseband receivedsignals 300 which are delayed by the delay units 166 by the weightingcoefficients 322. The summing unit 170 sums up the whole results of themultiplications by the multiplications units 168.

[0117] Hereunder will be described the operation of the receiver 106having the structure described above. The signals received by theplurality of antennas 134 are translated to the baseband receivedsignals 300 by the quadrature detection and so forth. When the risingedge detection unit 122 detects the starts of the burst signals from thebaseband received signals 300, the interval of the training signal 302is started. At the start timing of the interval of the training signal302, the antenna determination unit 10 selects the one baseband receivedsignal 300. Then the initial weight data setting unit 12 sets theinitial weighting coefficients 320, where the only initial weightingcoefficient 320 corresponding to the selected baseband received signal300 is made effective.

[0118] In the interval of the training signal 302, the weight switchingunit 18 outputs the initial weighting coefficients 320 as the weightingcoefficients 322 and the synthesizing unit 118 sums up the basebandreceived signals 300 weighting them with the weighting coefficients 322.Meanwhile, the weight computation units 120 update the control weightingcoefficients 310 by the LMS algorithm. In the interval of the datasignal, the gap compensating unit 16 compensates the control weightingcoefficients 310 with the gap error signal 316 computed in the gapmeasuring unit 14 and then outputs them as the updated weightingcoefficients 318. Moreover, the weight switching unit 18 outputs theupdated weighting coefficients 318 as the weighting coefficients 322 andthe synthesizing unit 118 weights the baseband received signals 300 withthe weighting coefficients 322 and sums them up.

[0119] According to the first embodiment, the processing delay can bereduced since the synthesizing processing is performed even in theinterval of the training signal regardless of the convergence of theweighting coefficients. Moreover, communications with surrounding radiostations located in the vicinity can be realized since the omni antennapattern is utilized for the weighting coefficients in the interval ofthe training signal. The weighting coefficients can be smoothly switchedbetween the omni antenna pattern and the adaptive array antenna pattern.

[0120] Second Embodiment

[0121] In the second embodiment, same as the first embodiment, receivedsignals are weighted with weighting coefficients and synthesized. Theprocessing delay hardly occurs since the switching is performed betweenthe omni antenna pattern which is precedently prepared and the adaptivearray pattern updated by the LMS algorithm. In the first embodiment, theswitching of the weighting coefficients between two types is performedin an undifferentiated manner at the timing where the training signalincluded in the burst signal ends. On the other hand, in the secondembodiment, the switching of weighting coefficients between two types isperformed adaptively at the timing where the LMS algorithm convergeswithin a predetermined range.

[0122]FIG. 16 shows the structure of the receiver 106 according to thesecond embodiment. The structure thereof is almost same as the structureof the receiver 106 shown in FIG. 4. However, the receiver 106 shown inFIG. 16 includes a first convergence information 324 a, a secondconvergence information 324 b, . . . and a n-th convergence information324 n which are generically named convergence information 324.

[0123] The weight switching unit 18 shown in FIG. 4 performs theswitching operation in a manner that the initial weighting coefficient320 is selected in the interval of the training signal 302 and theupdated weighting coefficient is selected in the interval of the datasignal, wherein the end timing of the interval of the initial weightingcoefficients 320 severs as a trigger for the weight switching unit 18.On the other hand, the weight switching unit 18 utilizes the timingwhere the control weighting coefficients 310 converge in the weightcomputation units 120 (hereinafter this timing is referred to as a“convergence timing”). The convergence timing is generated by thecontrol unit 124 when the fluctuation of the control weightingcoefficients 310 caused by updating them converges within in a range,wherein the range is determined precedently. Alternatively, theconvergence timing may be generated by the control unit 124 when theupdated error signal 308 becomes within a range, wherein the range ispredetermined for the error signal 308.

[0124] The control unit 124 notifies the convergence timing to each unitin accordance with the necessity, and each unit performs its assignedprocessing according to the convergence timing.

[0125]FIG. 17 shows the structure of the antenna determination unit 10.The antenna determination unit 10 includes a switching unit 72, a levelmeasuring unit 74, a storage 76 and a selecting unit 24.

[0126] The switching unit 72 switches the plurality of baseband receivedsignals 300 at a prescribed timing and outputs one baseband receivedsignal 300. The switching may be performed on the plurality of burstsignals.

[0127] The level measuring unit 74 measures the electric power of thebaseband received signal 300 selected by the switching unit 72. Beingdifferent from the antenna determination unit 10 shown in FIG. 11, theelectric power of the plurality of baseband received signals 300 is notmeasured at a time but measured for every baseband received signal 300one by one, therefore the size of an arithmetic circuit for the levelmeasuring unit 74 can be diminished.

[0128] The storage 76 stores the computed electric power of the basebandreceived signal 300.

[0129]FIG. 18 shows the structure of the gap measuring unit 14. The gapmeasuring unit 14 shown in FIG. 18 is structured by adding a frequencyerror estimation unit 78, an interval measuring unit 80, amultiplication unit 82, a complex number transformation unit 84, acomplex conjugate unit 86 and a multiplication unit 88 to the gapmeasuring unit 14 shown in FIG. 13.

[0130] In the second embodiment, being different from the firstembodiment, the timing where the weight computation units 120 startupdating the control weight coefficients 310 is the head of the longpreamble of the burst format shown in FIG. 3. The control weightingcoefficient 310 wi updated from the head of the long preamble is givenby the expression (5) below. Here, it is presumed that the controlweighting coefficients 310 have converged sufficiently.

Σh _(i) W _(i) exp(jΔωsT)=1  (5)

[0131] Here, sT is the time length of a short preamble interval. Byperforming the synthesizing processing based on the expression (5), thesynthesis result is given by:

y(t)=S(t)exp (jΔωt)exp(jΔωsT)+n (t)  (6)

[0132] By comparing these expressions, the gap error signal 316C can beexpressed as follows.

C=h _(i) exp(−j ΔωsT)  (7)

[0133] The frequency error estimation unit 78 estimates a frequencyerror Δω based on the baseband received signals 300. The intervalmeasuring unit 80 measures the time sT of the short preamble intervalbased on the training signal 302.

[0134] The multiplication unit 82 multiplies the frequency error by thetime of the short preamble interval and acquires the phase error in theinterval of the short preamble. This phase error is transformed to acomplex number by the complex number transformation unit 84 and acomplex conjugate processing is performed thereon by the complexconjugate unit 86.

[0135] The multiplication unit 88 multiplies, by the above-describedphase error, the result of the multiplication processing on the onebaseband received signal 300 and the complex conjugated training signal302, and then generates the gap error signal 316.

[0136]FIG. 19 shows the structure of the frequency error estimation unit78. The frequency error estimation unit 78 includes: a first main signaldelay unit 26 a, a second main signal delay unit 26 b, . . . and a n-thmain signal delay unit 26 n which are generically named main signaldelay units 26; a first multiplication unit 28 a, a secondmultiplication unit 28 b, . . . and a n-th multiplication unit 28 nwhich are generically named multiplication units 28; a first delay unit30 a, a second delay unit 30 b, . . . and a n-th delay unit 30 n whichare generically named delay units 30; a first complex conjugate unit 32a, a second complex conjugate unit 32 b, . . . and a n-th complexconjugate unit 32 n which are generically named complex conjugate units32; a first multiplication unit 34 a, a second multiplication unit 34 b,. . . and a n-th multiplication unit 34 n which are generically namedmultiplication units 34; an averaging unit 36; a phase transformationunit 38; and a training signal memory 42.

[0137] The multiplication units 28 acquires a received signal Zi(t)which does not include transmission signal component by multiplying thebaseband received signals 300 delayed in the main signal delay units 26by the training signal 302 after the complex conjugate transform. Thereceived signal Zi(t) is given by: $\begin{matrix}\begin{matrix}{{Z_{i}(t)} = {{x_{i}(t)}{S^{*}(t)}}} \\{= {h_{i}{\exp \left( {{j\Delta}\quad \omega \quad t} \right)}}}\end{matrix} & (8)\end{matrix}$

[0138] Here, it is assumed that a noise is sufficiently small andtherefore the noise is ignored.

[0139] The delay units 30 and the complex conjugate units 32 delay theZi(t) and then transform the Zi(t) to the complex conjugate. The Zi(t)transformed to the complex conjugate is multiplied by the original Zi(t)in the multiplication units 34. The result Ai of the multiplication isgiven by: $\begin{matrix}\begin{matrix}{{A_{i}(t)} = {{Z_{i}(t)}{Z_{i}^{*}\left( {t - T} \right)}}} \\{= {\exp \left( {{j\Delta}\quad \omega \quad t} \right)}}\end{matrix} & (9)\end{matrix}$

[0140] Here, the delay time of the delay units 30 is set to the symbolinterval T.

[0141] The averaging unit 36 averages the multiplication resultscorresponding to each antenna. The multiplication results of which thetime is shifted may also be utilized.

[0142] The phase transformation unit 38 transforms the averagedmultiplication result A to a phase signal B by utilizing an arc tangentROM.

B=ΔωT  (10)

[0143]FIG. 20 shows the structure of a gap measuring unit 14 which isdifferent from the gap measuring unit 14 shown in FIG. 18. The gapmeasuring unit 14 shown in FIG. 20 is structured by adding a counterunit 90, a multiplication unit 92, a complex number transformation unit94, a summing unit 96, a summing unit 98 and a division unit 40 to thegap measuring unit 14 shown in FIG. 18. In the gap measuring unit 14shown in FIG. 18, the multiplication of the baseband received signals300 by the training signal 302 is performed only on the head signal ofthe burst signal. On the other hand, in the gap measuring unit 14 shownin FIG. 20, the multiplications are performed during prescribed time andthe results thereof are averaged.

[0144] The summing unit 98 sums up the results of the multiplications bythe multiplications unit 96 during prescribed time interval (hereinafterreferred to as “averaging time”) in order to average the results of themultiplications of the baseband received signals 300 by the trainingsignal 302.

[0145] The counter unit 90 counts up the symbol intervals in order toacquire the phase error corresponding to the averaging time based on thefrequency error outputted from the frequency error estimation unit 78.The multiplication unit 92 acquires the phase error corresponding toeach counter value by respectively multiplying each counter value by thefrequency error. The phase errors are transformed to complex numbers inthe complex number transformation unit 94 and are summed up in thesumming unit 96 within the averaging time.

[0146] The division unit 40 divides the results of the multiplicationssummed up by the summing unit 98 with the phase errors summed up by thesumming unit 96. The succeeding processings are same as those of the gapmeasuring unit 14 shown in FIG. 18.

[0147] Hereunder will be described the operation of the receiver 106having the structure described above. The signals received by theplurality of antennas 134 are transformed to the baseband receivedsignals 300 by the quadrature detection and so forth. When the risingedge detection unit 122 detects the start timings of the burst signalsfrom the baseband received signals 300, the interval of the trainingsignal 302 is started. At the start timing of the interval of thetraining signal 302, the antenna determination unit 10 selects the onebaseband received signal 300 and the initial weight data setting unit 12sets the initial weighting coefficients 320 among which only the oneinitial weighting coefficient 320 corresponding to the selected basebandreceived signal 300 is made effective. Thereafter, the weight switchingunit 18 outputs the initial weighting coefficients 320 as the weightingcoefficients 322 and the synthesizing unit 118 weights the basebandreceived signals 300 with the weighting coefficients 322 and sums themup.

[0148] Meanwhile, the weight computation units 120 update the controlweighting coefficients 310 by the LMS algorithm. When the controlweighting coefficients 310 converge within the prescribed range, the gapcompensating unit 16 compensates the control weighting coefficients 310with the gap error signal 316 computed in the gap measuring unit 14according to the instruction from the control unit 124 and then outputsthem as the updated weighting coefficients 318. Moreover, weightswitching unit 18 outputs the updated weighting coefficients 318 as theweighting coefficients 322 and the synthesizing unit 118 weights thebaseband received signals 300 with the weighting coefficients 322 andsums them up.

[0149] According to the second embodiment, the synthesis processing isperformed regardless of the convergence of the weighting coefficientseven in the interval of the training signal. Therefore, the processingdelay can be reduced. Moreover, in the case that the adaptive algorithmconverges during the training signal interval, the responsecharacteristic can be improved by reflecting it to the weightingcoefficients. This is because the switching of the weightingcoefficients between two types is performed based on the convergencetiming of the adaptive algorithm.

[0150] Although the present invention has been described by way ofexemplary embodiments, it should be understood that many changes andsubstitutions may be made by those skilled in the art without departingfrom the scope of the present invention which is defined by the appendedclaims.

[0151] In the embodiments, the initial weight data setting unit 12 setsthe effective value for the initial weighting coefficient 320 for theone baseband received signal 300 selected by the antenna determinationunit 10, which has the largest electric power, and the unit 12 sets thevalue which is not effective for the other initial weightingcoefficients 320. The initial weighting coefficients 320, however, donot necessarily need to be set based on the electric power. For example,one fixed initial weighting coefficient 320 may be set to the effectivevalue and the other initial weighting coefficients 320 may be set to thevalue that is not effective. In that case, the antenna determinationunit 10 becomes unnecessary.

[0152] In the embodiments, the initial weight data setting unit 12 setsthe effective value for the initial weighting coefficient 320 for theone baseband received signal 300 selected by the antenna determinationunit 10, which has the largest electric power, and the unit 12 sets thevalue which is not effective for the other initial weightingcoefficients 320. It is, however, not necessarily required to set theweighting of the omni antenna pattern for the initial weightingcoefficients 320. For example, the setting may be performed on theupdated weighting coefficients 318 or the control weighting coefficients310 which are utilized in the already received burst signal. When thefluctuation of the radio transmission environment is small, it isestimated that this setting will not cause a serious degradation of theresponse characteristic.

[0153] In the embodiments, the weight computation units 120 utilize theLMS algorithm as the adaptive algorithm. However, another algorithm suchas the RLS algorithm may be utilized. Moreover, the weightingcoefficients may not be updated. That is, it is sufficient if theadaptive algorithm is selected in accordance with the estimated radiotransmission environment, the size of arithmetic circuits or the like.

[0154] In the first embodiment, the rising edge detection unit 122computes the electric power of the baseband received signals 300 anddetects the rising edge of the burst signal based on the computationresult. The rising edge of the burst signal may be, however, detected byimplementing another structure. For example, the rising edge may bedetected by a matched filter which is shown as the structure of thetiming detection unit 144. That is, it is sufficient if the rising edgeof the burst signal is detected accurately.

[0155] In the first embodiment, the training signal interval is the timewhere the initial weighting coefficients 320 are changed into theweighting coefficients 322. However, the time does not need to belimited to the interval of the training signal. For example, the timemay be shorter than the interval of the training signal. That is, thetime can be set according to the length of the interval of the trainingsignal and to the required estimation accuracy.

[0156] In the second embodiment, the delay time of the delay units 30which are included in the frequency error estimating unit 78 is set to 1symbol. The delay time, however, is not limited to 1 symbol. Forexample, the delay time may be 2 symbols or may be symbols in theinterval between the start and end of the training signal. That is, itis sufficient if an optimum delay time of the delay units 30 is decidedin accordance with the stability of the frequency oscillator and withthe required accuracy of the frequency offset estimation.

What is claimed is:
 1. A receiver, including: an input unit which inputsa plurality of signals on which a processing is to be performed; aswitching unit which switches a plurality of weighting coefficients bywhich the plurality of inputted signals are multiplied between aplurality of first weighting coefficients to be temporarily utilized anda plurality of second weighting coefficients which have higheradaptabilities; a controller which instructs the switching unit toswitch the weighting coefficients between the plurality of firstweighting coefficients and the plurality of second weightingcoefficients; and a synthesizer which synthesizes results ofmultiplications, where the multiplications are performed on theplurality of inputted signals and the plurality of weightingcoefficients.
 2. A receiver, includes: an input unit which inputs aplurality of signals on which a processing is to be performed; aswitching unit which switches a plurality of weighting coefficients bywhich the plurality of inputted signals are multiplied between aplurality of first weighting coefficients and a plurality of secondweighting coefficients; a controller which instructs the switching unitto switch the weighting coefficients between the plurality of firstweighting coefficients and the plurality of second weightingcoefficients in a prescribed interval, where the plurality of signalsare inputted in a sequential manner during the interval; and asynthesizer which synthesizes results of multiplications, where themultiplications are performed on the plurality of inputted signals andthe plurality of weighting coefficients.
 3. A receiver according toclaim 2, wherein the plurality of first weighting coefficients is set ina manner that, as results of multiplications by the plurality ofinputted signals, a multiplication result corresponding to one signalamong the plurality of inputted signals becomes effective.
 4. A receiveraccording to claim 3, wherein the one signal among the plurality ofinputted signals is a signal having a largest value among the pluralityof inputted signals.
 5. A receiver according to claim 2, wherein theplurality of first weighting coefficients is set by utilizing theplurality of second weighting coefficients which have already been set.6. A receiver according to claim 2, further including: a weightingcoefficient updating unit which updates a plurality of third weightingcoefficients adaptively based on the plurality of inputted signals; agap estimator which estimates gaps between the plurality of firstweighting coefficients and the plurality of third weighting coefficientsby performing a correlation processing between at least one of theplurality of inputted signals and a known signal; and a gap compensatorwhich generates the plurality of second weighting coefficients bycompensating the plurality of third weighting coefficients based on theestimated gaps.
 7. A receiver according to claim 2, wherein the signalsinputted during the prescribed interval in the sequential manner includesignals having different characteristics, and wherein the controllerinstructs to switch the weighting coefficients between the firstweighting coefficients and the second weighting coefficients when it isdetected a shift point where the characteristics of the signals change.8. A receiver according to claim 6, wherein the controller inputssequentially the plurality of third weighting coefficients updated inthe weight coefficient updating unit and instructs the switching unit toswitch the weighting coefficients between the first weightingcoefficients and the second weighting coefficients when fluctuation ofthe plurality of third weighting coefficients converges within aprescribed range.
 9. A receiving method, including: inputting aplurality of signals on which a processing is to be performed; switchinga plurality of weighting coefficients by which the plurality of inputtedsignals are multiplied between a plurality of first weightingcoefficients to be temporarily utilized and a plurality of a secondweighting coefficients which have higher adaptabilities; giving aninstruction of switching the weighting coefficients between theplurality of first weighting coefficients and the plurality of secondweighting coefficients; and synthesizing results of multiplications,where the multiplications are performed on the plurality of inputtedsignals and the plurality of weighting coefficients.
 10. A receivingmethod, including: inputting a plurality of signals on which aprocessing is to be performed; switching a plurality of weightingcoefficients by which the plurality of inputted signals are multipliedbetween a plurality of first weighting coefficients and a plurality ofsecond weighting coefficients; giving an instruction of switching theweighting coefficients between the plurality of first weightingcoefficients and the plurality of second weighting coefficients in aprescribed interval, where the plurality of signals are inputted in asequential manner during the interval; and synthesizing results ofmultiplications, where the multiplications are performed on theplurality of inputted signals and the plurality of weightingcoefficients.
 11. A receiving method according to claim 10, wherein theplurality of first weighting coefficients is set in a manner that, asresults of multiplications by the plurality of inputted signals, amultiplication result corresponding to one signal among the plurality ofinputted signals becomes effective.
 12. A receiving method according toclaim 11, wherein the one signal among the plurality of inputted signalsis a signal having a largest value among the plurality of inputtedsignals.
 13. A receiving method according to claim 10, wherein theplurality of first weighting coefficients may be set by utilizing theplurality of second weighting coefficients which have already been set.14. A receiving method according to claim 10, further including:updating a plurality of third weighting coefficients adaptively based onthe plurality of inputted signals; estimating gaps between the pluralityof first weighting coefficients and the plurality of third weightingcoefficients by performing a correlation processing between at least oneof the plurality of inputted signals and a known signal; and generatingthe plurality of second weighting coefficients by compensating theplurality of third weighting coefficients based on the estimated gaps.15. A receiving method according to claim 10, wherein the signalsinputted during the prescribed interval in the sequential manner includesignals having different characteristics and wherein, in giving theinstruction of switching the weighting coefficients between the firstweighting coefficients and the second weighting coefficients, theinstruction is given when it is detected a shift point where thecharacteristics of the signals change.
 16. A receiving method accordingto claim 14, wherein the plurality of third weighting coefficientsupdated is inputted sequentially in giving the instruction of switchingthe weighting coefficients between the first weighting coefficients andthe second weighting coefficients, and the instruction is given whenfluctuation of the plurality of third weighting coefficients convergeswithin a prescribed range.
 17. A program executable by a computer,including: inputting a plurality of signals on which a processing is tobe performed; switching a plurality of weighting coefficients by whichthe plurality of inputted signals are multiplied between a plurality offirst weighting coefficients to be temporarily utilized and a pluralityof a second weighting coefficients which have higher adaptabilities;giving an instruction of switching the weighting coefficients betweenthe plurality of first weighting coefficients and the plurality ofsecond weighting coefficients; and synthesizing results ofmultiplications, where the multiplications are performed on theplurality of inputted signals and the plurality of weightingcoefficients.
 18. A program executable by a computer, including:inputting a plurality of signals on which a processing is to beperformed; switching a plurality of weighting coefficients by which theplurality of inputted signals are multiplied between a plurality offirst weighting coefficients and a plurality of second weightingcoefficients; giving an instruction of switching the weightingcoefficients between the plurality of first weighting coefficients andthe plurality of second weighting coefficients in a prescribed interval,where the plurality of signals are inputted in a sequential mannerduring the interval; and synthesizing results of multiplications, wherethe multiplications are performed on the plurality of inputted signalsand the plurality of weighting coefficients.
 19. A program according toclaim 18, wherein the plurality of first weighting coefficients is setin a manner that, as results of multiplications by the plurality ofinputted signals, a multiplication result corresponding to one signalamong the plurality of inputted signals becomes effective.
 20. A programaccording to claim 19, wherein the one signal among the plurality ofinputted signals is a signal having a largest value among the pluralityof inputted signals.
 21. A program according to claim 18, wherein theplurality of first weighting coefficients may be set by utilizing theplurality of second weighting coefficients which have already been set.22. A program according to claim 18, further including: updating aplurality of third weighting coefficients adaptively based on theplurality of inputted signals; estimating gaps between the plurality offirst weighting coefficients and the plurality of third weightingcoefficients by performing a correlation processing between at least oneof the plurality of inputted signals and a known signal; and generatingthe plurality of second weighting coefficients by compensating theplurality of third weighting coefficients based on the estimated gaps.23. A program according to claim 18, wherein the signals inputted duringthe prescribed interval in the sequential manner include signals havingdifferent characteristics and wherein, in giving the instruction ofswitching the weighting coefficients between the first weightingcoefficients and the second weighting coefficients, the instruction isgiven when it is detected a shift point where the characteristics of thesignals change.
 24. A receiving method according to claim 22, whereinthe plurality of third weighting coefficients updated is inputtedsequentially in giving the instruction of switching the weightingcoefficients between the first weighting coefficients and the secondweighting coefficients, and the instruction is given when fluctuation ofthe plurality of third weighting coefficients converges within aprescribed range.